ABSTRACT Approximately 20% of adolescents aged 12-19 are obese. Overweight and obesity in adolescents are associated with numerous health and psychosocial consequences that can carry forward into adulthood. Developmentally, adolescence is a period of significant biological and physical changes, as well as emotional development. Emotion regulation is critical in managing interactions with others, and thus reflects an important task for adolescents. Adolescents who lack adaptive emotion regulation skills may turn to eating to regulate emotions and provide momentary relief of negative affect. Emotional eating is in fact associated with depression, binge eating and obesity. Current behavioral weight loss (BWL) treatment for adolescent obesity does not address emotions and produces variable weight-loss results with high attrition. Incorporating a treatment that targets emotion regulation may provide the skills needed to reduce emotional eating and encourage greater weight loss. Dialectical Behavior Therapy (DBT) is an evidence-based treatment that targets emotion regulation. We have created a new treatment model, Preventing Emotional Eating Routines (PEER) that targets both emotion regulation and weight loss by incorporating DBT skills with BWL, as well as an emotion-focused parent training program. Our pilot data suggests that PEER is a promising treatment for overweight and obese adolescents and their parents. The objective of this proposed study is to further evaluate the PEER program with overweight and obese adolescents and their parents. We will recruit and randomize 160 adolescents and their parents to either PEER or standard BWL at two sites ? University of California, San Diego and University of Minnesota. Treatment will take place in groups over the course of 6 months. Assessments will be conducted at baseline, mid-treatment, post-treatment, 6-month follow-up, and 12-month follow-up. Primary Aims include to evaluate the efficacy of PEER compared to BWL on adolescent weight loss (Aim 1), emotion regulation and emotional eating (Aim 2). Secondary Aims include examining differences between PEER and BWL on parent BMI, parent emotion regulation, parent emotional eating, and the parent- child relationship. Lastly, we will explore moderators and mediators of adolescent weight loss, as well as emotion phenotypes. This application is a critical next step in the development of a treatment for adolescent obesity targeting emotion regulation and emotional eating as a mechanism of action.